Semantic Convergence: Investigating Shared Representations Across Scaled LLMs

Abstract: We investigate feature universality in Gemma-2 LLMs (Gemma-2-2B and Gemma-2-9B), asking whether models with a four-fold difference in scale still converge on comparable internal concepts. Using the Sparse Autoencoder (SAE) dictionary-learning pipeline, we utilize SAEs on each model's residual-stream activations, align the resulting monosemantic features via activation correlation, and compare the matched feature spaces with SVCCA and RSA. Middle layers yield the strongest overlap, while early and late layers show far less similarity. Preliminary experiments extend the analysis from single tokens to multi-token subspaces, showing that semantically similar subspaces interact similarly with LLMs. These results strengthen the case that LLMs carve the world into broadly similar, interpretable features despite size differences, reinforcing universality as a foundation for cross-model interpretability.